Published Version

Abstract

Growth rates of new particles during coastal and marine secondary aerosol particle formation events were studied in western Ireland, both at the Mace Head atmospheric research station and onboard the R/V Celtic Explorer as part of the Marine Aerosol Production project. Strong new particle formation events are frequently detected at Mace Head caused by the emission of precursor gases from exposed seaweed during low tide. Although these events were usually only detected as a mode of particles at a certain size, we were able to link the size of the mode to the growth time of these particles after the initial formation by combining data from several events measured between January 2006 and November 2007 with an air ion spectrometer. Typically, the early growth rates were extremely high, reaching values of several hundred nanometers per hour during the first seconds. The growth rates rapidly decreased and reached values below 1 nm h(-1) within 1 h after nucleation. Our results were reproduced with box model calculations. All the obtained growth rates could be explained by the model either by varying the precursor formation time (typically a few seconds) or allowing multiple precursor vapor additions. From the ship-borne measurements, we report the first observations of purely open ocean new particle formation detected in this region. In total, four events were detected during this period, with three having a variable continental influence. An estimated average growth rate in marine conditions was 3 nm h(-1) for these events.